Open circuit voltage (OCV) of electrical devices is an issue in various fields, whose numerical evaluation needs careful treatment. The open-circuited structure is ill-conditioned because of the singular electric field at the corners, and the TEM component of the electric field has to be extracted before integrated to give the voltage in the direct method of obtaining the OCV. This paper introduces the indirect methods to calculate the OCV, the admittance matrix method and the Norton theorem method. Both methods are based on the short-circuited structure which is well-conditioned. The explicit expressions of the OCV are derived in terms of the admittance matrix elements in the admittance matrix method, and in terms of the short circuit current and the antenna impedance of the electrical device under consideration in the Norton theorem method. These two methods are equivalent in theory, but the admittance matrix method is suitable for the nearby transmitter cases while the Norton theorem method is suitable for the distant transmitter cases. Several examples are given to show the usefulness of the present theory.

Formation of thin insulating SiO2 films by anodic oxidation of silicon was studied as a part of investigating an alternative method of fabricating low-cost silicon MIS solar cells. Anodization in the constant-voltage mode was carried out in nonaqueous ethylene glycol solution. The film thickness was carefully measured using an ellipsometer of wavelength 6238 . MIS cell performance was evaluated by comparing the open circuit voltage VOC and the short circuit current density ISC with those of the bare Schottky cell (without anodization) under illumination by a tungsten lamp. It was found that anodization in the constant-voltage mode can increase VOC without reducing ISC, and that anodization in the constant-voltage mode is more controllable and reproducible. The optimun formation voltage which gives the maximum VOC of the MIS cell depends on the forming voltage of oxide. A brief discussion on the mechanism for VOC increase is given.